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Disturbances control the landscape-level C dynamics of boreal forests, but post-disturbance C dynamics are usually poorly quantified. In the current study, we use 10 years of [CO.sub.2] flux measurements at a boreal black spruce (Picea mariana (Mill.) B.S.P.) cutover in eastern Canada to estimate time to C neutrality, quantify the relative role of respiration versus photosynthesis during recovery, and determine the agreement between cumulated [CO.sub.2] fluxes and plot-level changes in C content. The site was a net source of 139 g C*[m.sup.-2]*[year.sup.-1] 2 years post-harvest, dropped further to a source of 173 g C*[m.sup.12]*[year.sup.-1] 4 years post-harvest, following a scarification treatment, and was nearly C neutral 10 years post-harvest. Gross ecosystem productivity (GEP) increased by 50 g C*[m.sup.12]*[year.sup.-1] post-scarification, while ecosystem respiration (ER) increased by only 23 g C*[m.sup.12]*[year.sup.-1]. The resulting net rate of increase of 27 g C*[m.sup.12]*[year.sup.-1] in net ecosystem productivity was driven by changes in increasing leaf area. In fact, vegetation regrowth had a much greater impact on annual fluxes than did interannual variability in climate. Biometric-based measurements of total C losses after harvest were in relatively good agreement with eddy-covariance-based estimates 8 years after the harvest. Resume: Les perturbations controlent la dynamique du C a l'echelle du paysage dans les forets boreales mais la dynamique du C apres perturbation est generalement mal quantifiee. Dans cette etude, nous avons utilise des mesures de flux de [CO.sub.2] prises pendant 10 ans apres une coupe a blanc dans une foret boreale d'epinette noire (Picea mariana (Mill.) B.S.P.) situee dans l'Est du Canada dans le but d'estimer le temps necessaire pour atteindre la neutralite en C, de quantifier le role de la respiration relativement a celui de la photosynthese durant la periode de recuperation et de verifier la concordance entre les flux cumules de [CO.sub.2] et les changements dans le contenu en C a l'echelle de la place ette echantillon. Le site etait une source nette de 139 g C*[m.sup.-2]*[an.sup.-1] 2 ans apres la recolte, puis une source plus importante de 173 g C*[m.sup.-2]*[an.sup.-1] 4 ans apres la recolte suite a un scarifiage et avait presque atteint la neutralite en C 10 ans apres la recolte. La productivite brute de l'ecosysteme a augmente de 50 g C*[m.sup.-2]*[an.sup.-1] apres le scarifiage tandis que la respiration de l'ecosysteme a augmente de seulement 23 g C*[m.sup.-2]*[an.sup.-1]. Il en resulte un taux d'augmentation de la productivite nette de l'ecosysteme de 27 g C*[m.sup.-2]*[an.sup.-1] du a l'augmentation de la surface foliaire. En fait, la repousse de la vegetation a eu un impact beaucoup plus grand sur les flux annuels que la variabilite interannuelle du climat. Les mesures de nature biometrique des pertes de C total apres la recolte correspondent relativement bien aux estimations basees sur la covariance des turbulences 8 ans apres la recolte. [Traduit par la Redaction], Introduction The boreal forest is the second largest forested biome on Earth (Landsberg and Gower 1997) and the largest in Canada (Kurz and Apps 1999). Globally, boreal forests contain about [...]

Abstract: Net ecosystem productivity (NEP) during August 2003 was measured by using eddy covariance above 17 forest and 3 peatland sites along an east-west continental-scale transect in Canada. Measured sites [...]

Examines the effects of induced root freezing on the growth and physiology of boreal conifer seedlings. Decrease of stomatal conductance; Reduction in nitrogen concentration of current-year foliage; Indication of reduced in annual height increment of white spruce.